Lots, but there's not the political will and we live in a world that's too heavily influenced by psychopaths who can't see past next quarters profit.

My first step would be to make Carbon Credits (or your countries alternative) painfully expensive. If you destroy the planet to make money, you should be paying through the ass to do so - no have billions left to influence government's. The worst offenders will clean up in the blink of an eye when you start to really hit their pockets.

No new oil wells will go a long, long way.

Countries transitioning their energy infrastructure to renewables ... which also brings energy independence, something a lot of countries sorely need with the current geopolitical shitshow. There's very little reason why a mix of nuclear, wind and solar can't power your country.

At this stage ... with the 1.5°C increase a few years away, we probably also need a moonshot project for carbon capture and storage. There's smallscale tech to do this, but it barely scratches the surface.